ci: include 8.0

.github/workflows/tests.yml

@@ -32,7 +32,7 @@ jobs:
         # Only test the latest major release of Sphinx because otherwise we need to
         # keep multiple versions of regression tests on file and this creates lots of
         # noise in the tests.
-        sphinx: ["~=5.0","~=6.0","~=7.0"]
+        sphinx: ["~=6.0","~=7.0", "~8.0"]
         include:
         - os: windows-latest
           # Python 3.12 is broken on windows builds until the following PR is released: